How the 'physical and chemical properties' of the substance may change, when it is converted to "nano size"

Question

Or how their characteristics may change?

Answer 1

When things are large, their properties can be described by classical physics (e.g., Newtonian physics, such as billiard balls that you can predict their path for eternity using very simple math). When things are very small, they are governed by quantum physics (e.g. the Heisenberg uncertainty principle: you can never know the momentum and position exactly). In a "nano size" you can span the range between these two types of behaviors, and really cool behaviors can result.